Merge Sort DSA

#include <iostream>
using namespace std;

void merge(int arr[], int left, int mid, int right) {
    int n1 = mid - left + 1;
    int n2 = right - mid;

    int L[n1], R[n2];

    for (int i = 0; i < n1; i++)
        L[i] = arr[left + i];
    for (int j = 0; j < n2; j++)
        R[j] = arr[mid + 1 + j];

    int i = 0;
    int j = 0;
    int k = left;

    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) {
            arr[k] = L[i];
            i++;
        } else {
            arr[k] = R[j];
            j++;
        }
        k++;
    }

    while (i < n1) {
        arr[k] = L[i];
        i++;
        k++;
    }

    while (j < n2) {
        arr[k] = R[j];
        j++;
        k++;
    }
}

void mergeSort(int arr[], int left, int right) {
    if (left >= right)
        return;

    int mid = left + (right - left) / 2;

    mergeSort(arr, left, mid);
    mergeSort(arr, mid + 1, right);

    merge(arr, left, mid, right);
}

int main() {
    int n ;
    cout<<"Enter size:-";
    cin>>n;
    int arr[n];
    //sizeof(arr) / sizeof(arr[0]);
    cout<<endl;
    cout<<"enter elements:\n";
    for(int i;i<n;i++){
        cin>>arr[i];
    }
    mergeSort(arr, 0, n - 1);

    cout << "Sorted array: \n";
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
    cout << endl;

    return 0;
}